When firearms, such as pistols, rifles, and other similar weaponry, are fired, minute amounts of lead, copper, carbon, and other such fouling residue is frequently deposited within the bores and other interior parts of the firearms. Over a period of time, such residue builds up to the extent that the accuracy of the firearm and the integrity of the ferrous metal bore and other interior parts is adversely affected. In addition, a build up of fouling residue poses a significant hazard to a user should the fouling residue cause blockage of, and subsequent explosion within, the bore. Hence, it is necessary to periodically remove the metal and nonmetal fouling residue from the bore of a firearm.
Bore cleaning methods are well established in the prior art and, in general, include various combinations of mechanical abrasion and chemical oxidation or dissolution of the residue. Similar prior art methods and materials have been used both for conventional firearms, like those used for hurting and target shooting, and larger or more sophisticated weapons, such as those used in military or police applications. Unfortunately, the conventional bore cleaning process is characterized by tedious and time-consuming work. In addition, many of the cleaning solvents pose significant health hazards due to their volatility and/or toxicity.
Metal residue is the most difficult of the fouling residues to remove from the bore of a firearm. Metal residue may include layers of lead or lead alloy from firing lead or partially-jacketed bullets; and/or copper, gliding metal or other copper alloy metals from jacketed bullets. The layers of metal residue are most commonly removed by wetting the interior of the bore with a solvent or penetrant which dissolves or loosens the metal residue. Various types of brushes are frequently used to aid loosening. The residue is then removed from the bore with a cloth patch or a cleaning rod. For harder or thicker metal layers, abrasive cleaners applied with a patch or metal-bristled brush, with or without solvents, are often used. Unfortunately, the cleaners, solvents, and brushes can undesirably pit or otherwise damage the ferrous metal bore.
A prior art method used to remove lead deposits involves treating the bore with mercury to form a lead-mercury amalgam which loosens and/or dissolves the lead from the bore for relatively easy removal. However, the high toxicity and hazards related to the handling and use of mercury are well known and this method is, therefore, extremely unsafe, regardless of its efficacy.
Copper and copper alloy residues pose a particularly difficult cleaning problem due to the relatively strong electropositive nature of copper. A conventional method for removing copper or copper alloy deposits is to plug and fill the bore with an aqueous ammonia solution. The firearm, filled with the aqueous ammonia solution, is allowed to stand for several hours until the copper residue is chemically oxidized and dissolved. The bore is then brushed and swabbed as previously discussed. However, the ammonia concentration in some formulations is sufficiently high that contact with the eyes is dangerous and the evolution of noxious fumes can lead to respiratory injuries. In addition, conventional methods that employ ammonia derivatives, such as methylamine, or ammonia-based solutions such as ammonium persulfate, ammonium sulfate, and so forth, pose similar hazards and do little to alleviate the tedious and time-consuming process of cleaning the bore of a firearm.
Repeated cleaning of firearms by the foregoing methods, particularly those using abrasive brushing, measurably wear the ferrous bore surface, adversely affect performance and accuracy, and result in shorter useful life.
As an alternative to the previously discussed methods, some prior art methods have suggested the use of electrolysis to remove copper residue from the bore of a firearm. One such method involves an electrolytic bath consisting of sodium nitrate and chromic acid and the passage of an electric current through the electrolytic solution. The effect of such treatment is the migration of the negatively and positively charged ions, such as metal ions, to the positive and negative electrodes, respectively. Unfortunately, this electrolyte is highly oxidizing to iron and, at the current densities applied, results in unacceptable corrosion of the ferrous metal bore of the firearm.
A similar electrolytic stripping process for removing copper, nickel, or chromium coatings is a bath consisting of sodium nitrate and an alkali metal hydroxide to which sodium nitrite is added to prevent etching of the ferrous metal bore. However, this electrolytic solution is also highly oxidizing. In addition, the process operates at relatively high current densities and temperatures and requires the use of chemicals which pose substantial health hazards.
The cleaning methods that employ electrolysis necessitate the use of electrically powered equipment that may be inconvenient or pose an unacceptable cost to a user cleaning only one or a small number of firearms. In the case of military weaponry, the electrolytic bath and associated equipment is impractical and expensive for use in the field.